1. Field of the Invention
This invention relates to vibration motors for use in cameras, office machines, semiconductor device manufacture systems and the like and, more particularly, to a method of machining grooves into a vibration member of a vibration motor.
2. Description of the Related Art
Many vibration motors have already been proposed in which a piezoelectric element is attached to an elastic member to form a vibration member and electrical signals differing in phase are applied to the piezoelectric element to produce vibration waves, such as a traveling vibration wave, in the elastic member so that a member in contact with the elastic member, for example, a rotor, moves relatively by the vibration waves. Such vibration motors have been put to practical use for cameras and video apparatus because they have a comparatively large torque when rotated at a low speed.
In many of the vibration motors proposed, it has been proposed to form a plurality of grooves in the elastic member for magnifying the amplitude of the vibration of the elastic member. Each of these grooves extends in a direction perpendicular to the direction in which the vibration waves propagate. Such grooves are depicted at 1A in FIG. 4 for the case in which the elastic member is a circular member and the vibration waves induced therein travel along the circumference of the elastic member.
As shown in FIG. 5, ordinarily, grooves 1A are formed by moving a metal saw 5 in the direction of the arrow 5A, that is, a direction perpendicular to the direction of propagation of the vibration wave, while the elastic member is held fixed. A bottom 1C of each groove 1A is thereby formed so as to extend linearly.
In this conventional machining method, a burr 1D is undesirably formed at each groove, as shown in detail in FIG. 5.
This burr is hard because of work hardening, and it is necessary to scratch the burr off each groove by using a stainless steel brush or the like. Burr removal is particularly hindered because each burr is curled to a base 1E of the elastic member 1 making it difficult for the stainless steel brush to "bite" at the burr.
In the ordinary vibration motor, about 100 grooves 1A are formed in the elastic member 1. The time required for this scratching is about 100 seconds with respect to one elastic member, which greatly influences the manufacture cost.